Toilet rim blocks comprising two masses are known, for example from EP0791047 B1. A toilet rim block is described therein, in which one mass is surrounded at least in part by a further mass. Since both masses comprise the same active ingredient in different concentrations, upon rinsing and complete transition to the inner mass, there is a change in the concentration of the active ingredient. However, this change is sudden, and a continuous change is not possible using this technology without significant effort.
DE 102008028138 A1 discloses coated toilet rim blocks, in which the compositions of the toilet rim block and the coating thereof are separated. When first used, e.g. at the time of the first flush, no active ingredient is dispensed from the toilet rim block into the flushing water, but rather from the coating of said block. It is thus possible to adjust optical properties of the toilet rim block. Furthermore, WO 2010018006 proposes coating the toilet rim blocks in order to adjust optical properties.
WO 2006070209 discloses cylindrical toilet rim blocks that comprise a core. Said blocks are used mainly as in-tank cleansing blocks and are intended to be permanently in water.
WO 2012062914 describes multilayer toilet rim blocks, in which the different layers can have different effects.
An essential feature of the embodiments known from the prior art is that the transition between the layers is sudden, in particular when the transition is intended to be an indicator of consumption. No solution has yet been found for achieving a continuous change in the dispensing of the active ingredient.